A conventional controller of a fuel injection system calculates an optimum injection amount and an injection start timing and the like from various engine-related parameters. The, the fuel injection system supplies fuel to the engine by the injection amount obtained from the computation by drive-controlling the injector.
However, even if the accuracy of parts such as the injector is improved to the maximum, when the viscosity of the fuel supplied to the injector and/or fuel performance (e.g., a cetane value in the case of diesel engine, or an octane value in the case of gasoline engine) has been changed, the injection start timing, the injection amount, the combustion amount and the like change.
Then, an engine torque, obtained in correspondence with an accelerator opening changes. This causes degradation of drivability performance, causes difficulty in air-fuel ratio control with high accuracy, and further disturbs techniques for improving fuel cost to the maximum and improving exhaust gas performance to the maximum.